Second Messenger

The process of signal transduction is essential for cells to receive and respond to various external stimuli. Second messengers play important roles in this process, relaying signals from surface receptors to intracellular targets, ultimately leading to the activation of specific responses. Second messengers are generally small molecules that act as intermediaries, transmitting and amplifying signals in the cell. They are typically produced or activated in response to the binding of a ligand to a cell surface receptor, initiating a cascade of events that ultimately results in cellular responses. A key second messenger is cyclic adenosine monophosphate (cAMP). Upon activation of G-protein coupled receptors (GPCRs), an associated G-protein is activated, leading to the production of cAMP by the enzyme adenylyl cyclase. cAMP acts as a second messenger in this system by binding to and activating a downstream enzyme, protein kinase A (PKA), which then phosphorylates specific target protein substrates, triggering a wide range of cellular responses. For example, in skeletal muscle cells, cAMP signalling stimulates glycogen breakdown, thereby promoting the release of glucose for energy production. Another important second messenger is inositol trisphosphate (IP3). Activation of certain GPCRs or receptor tyrosine kinases (RTKs) leads to the hydrolysis of phosphatidylinositol bisphosphate (PIP2) by the lipid enzyme phospholipase C (PLC), generating IP3. IP3 diffuses through the cytoplasm and binds to IP3 receptors on the endoplasmic reticulum, resulting in the release of calcium ions (Ca²⁺) from intracellular stores. The increased intracellular Ca²⁺ concentration then acts as a signal to activate various proteins, including calcium/calmodulin-dependent protein kinases (CaMKs) and protein kinase C (PKC), which in turn regulate diverse cellular processes such as gene expression, secretion, and muscle contraction. Diacylglycerol (DAG) is another lipid (specifically, a glycerol molecule that contains two fatty acid chains) that is generated along with IP3 during the hydrolysis of PIP2 by PLC. By virtue of its lipophilic fatty acid side chains, DAG remains within the plasma membrane and activates PKC, which then translocates to the membrane in its active form upon binding to DAG. PKC then phosphorylates target proteins, initiating various cellular responses. Cyclic guanosine monophosphate (cGMP) is another nucleotide second messenger involved in signal transduction pathways triggered by nitric oxide (NO) and certain hormones. In response to NO, the enzyme guanylyl cyclase synthesizes cGMP from guanosine triphosphate (GTP). cGMP activates protein kinase G (PKG), which then phosphorylates various target proteins, leading to vasodilation, smooth muscle relaxation, and other physiological responses. cGMP is also involved in phototransduction in rod cells of the retina, where it acts as a second messenger in the signal transduction pathway from light activation to visual perception. Finally, calcium ions (Ca²⁺) themselves can also function as second messengers. In addition to release of Ca²⁺ from intracellular stores via IP3, extracellular Ca²⁺ influx through ion channels can also elevate intracellular Ca²⁺ levels. Calcium-binding proteins such as calmodulin can bind to Ca²⁺ and undergo conformational changes, enabling them to interact with and activate target proteins involved in diverse cellular processes, including muscle contraction, neuronal signalling, and gene expression. We offer a wide product range of research reagents for studying second messengers, including PDE2A antibodies, PDE4D antibodies, PDE8A antibodies, PDE4C antibodies, and CREB + CREM ELISA Kits. Explore our full second messengers product range below and discover more, for less. Alternatively, you can explore our Nucleotide Messenger and Lipid Messengers product ranges.